Very high-resolution infrared imagery of misaligned tungsten monoblock edge heating in the WEST tokamak

Interpretation of temperature distribution observed on W-ITER-like PFUs in WEST monitored with a very-high-resolution IR system

“…The emissivity drop observed from 0 to 4-5 mm is assumed to be caused by a higher net erosion in this specific area. A hypothesis is that it may be caused by the combination of Larmor radius [25] and sheath effects [26], that locally increase the heat load over a few mm at the LE vicinity as mentioned in [4] and [27]. This toroidal pattern was observed in all misaligned PFUs measured with or without chamfer.…”

“…Regarding the IR settings, during the C3 experimental campaign, a small wavelength infrared (SWIR) filter was used (give the wavelengths explicitly), and that implies a high temperature threshold that limited the studies to the hot leading edges only, over a toroidal extension of X mm. it was decided to use a MWIR filter to lower the temperature detection threshold in order to be able to study the thermal scene over a full MB length with moderate heat flux as achieved in WEST during the C3 experimental campaign [4]. As a result, the VHR temperature database was considerably extended.…”

“…The ITER-like PFUs were monitored by a very high-resolution (VHR) infra-red camera (see right panel of Figure 3) in the middle wavelength IR (MWIR) band: λ = 3.9 ± 0.1 µm during C4 experimental campaign [24]. GROSJEAN -30/11/2020 The shot #54934 studied here was performed during the dedicated experiments on the LE described in [4]. During the experiments, a ~4 MW flattop injected LH power was performed during 6s, to reach the thermal equilibrium of the PFU in order to simplify the thermal modeling required for the parallel heat flux analysis performed in [4].…”

“…GROSJEAN -30/11/2020 The shot #54934 studied here was performed during the dedicated experiments on the LE described in [4]. During the experiments, a ~4 MW flattop injected LH power was performed during 6s, to reach the thermal equilibrium of the PFU in order to simplify the thermal modeling required for the parallel heat flux analysis performed in [4]. The IR data presented in the left panel of Figure 4, are interesting and complex.…”

“…This effect is enhanced by possible misalignments between MBs [3] (see right panel of Figure 1). The WEST divertor is designed such that the plasma flowing along the magnetic field lines impacts the MB top surfaces at glancing angles (α ~ 2.5° in the shot presented in this study: #54934) [4]).…”